Small restructure: release notes

[internetisaiah]

Summary

Small restructure for release notes. "Previous releases" now lives in it's own sub-directory to make indexing easier in text editor/IDE. For example, in Intellij IDEA, each user can set specific directories to be ignored in their global searches. This will help with that.

Related PRs, issues, or features (optional)

• N/A

Metadata

• Adds new file(s)
• Edits existing file(s)
• Removes file(s)

PR contributor checklist

• My PR follows the Kobiton Docs contributor guidelines, meaning:

  • My content contains correct spelling and grammar.
  • My files are named and structured correctly.
  • My style and voice follows the Microsoft Style Guide.
  • I added all new pages to their section's nav.adoc file.
  • I removed all localizations (like en-us) from my URLs.